Image forming apparatuses have been known which form an image on a recording medium based on an image data and also form a test image for image adjustment in the margin of the recording medium where the image is not formed. The test image is a pattern image such as a test chart for example, and such test images enable detecting errors in image forming such as clogging of nozzles that jet ink to form an image.
For example, Patent Document 1 proposes dividing a test image into parts and forming them respectively in upper and lower margins in the conveying direction of a recording medium during image formation, so as to form the whole test image required for the recording medium.